Coal hydrogenation

ABSTRACT

A coal hydrogenation process employing an expanded particulate solids bed wherein the solids are derived from the coal which is placed in random motion by the upflow of a slurry of coal, hydrocarbon liquid and hydrogen to produce better than 80 percent conversion of coal to gas and liquid synthetic petroleum products. The particulate solids bed is derived from the coal being fed to the reaction zone.

United States Patent Ronald M. Walk Lawrence Township, Mercer Co.;

[72] Inventors References Cited UNITED STATES PATENTS Edwin S. Johanson, Princeton; Seymour B. AIPWLPNMHWJH oi NJ Re.25,770 4/1965 Johanson 208/10 [21] AppL No. 7 2 2,885,337 5/1959 Keith et a1. 208/8 [22] Filed 1969 Primary Examiner-Delbert E. Gantz palfimed 1971 Assistant Examiner-Veronica OKeefe Asslgnee Hydrocarbon Research, Inc. AtlorneysNathaniel Ely and Bruce E. Hosmer New York, N.Y.

[54] ggahg igf fi gf ABSTRACT: A coal hydrogenation process employing an exg panded particulate solids bed wherein the solids are derived [52] U.S. Cl 208/8, from the coal which is placed in random motion by the upflow 48/197 of a slurry of coal, hydrocarbon liquid and hydrogen to [51] Int. Cl C10g 1/14, produce better than 80 percent conversion of coal to gas and ClOg 1/06 liquid synthetic petroleum products. The particulate solids [50] Field of Search 208/8, 10 bed is derived from the coal being fed to the reaction zone.

2 Hydrogen Recycle High Cool Pressure 33 Separator IO Preparation Drying Grinding '39 Low Light Screening ssu Recovery Oil 50 42 I4 m g Reactor '5 Midd|e Oil 36 Slurry Slurry Gas T031 Mixing la Separator l6 T System (v Middle Oil 35/ 37 Solids 22 T 1 2e 24 Heater ATTOR Pressure Separator High Hydrogen Recycle Cool Slurry I w m e f m2 4| I ll 3 TLO L O M W3 www 8 6 M 4 m I 2 mm 8 6 4 w 5 U V 7 D e a. o o E W.8 m. f .8 6 LDIR 5 5 3 6 5 V V 4 9 w 4 3 L% w W b g 4/ (y V i 4 0 Se (2 M r 0 Ir 6 u e 1 R SP 2 w m zkW i 2 Preparation Drying Grinding Screening PATENTEUNUV |97| Slurry SEYMOUR B.ALPERT by mmg/ com. HYDROGENA'IION BACKGROUND OF THE INVENTION The hydroconversion of coal to produce more valuable fuel products has been actively carried out for a very substantial period of time. With the advent of the internal combustion engine and with relatively limited petroleum supplies in some countries of the world, technical efforts were accelerated to convert coal to liquid fuels. However, with the presently established low economic promise for such processes, this work has been continued on a very reduced scale. Even through the fundamental knowledge of coal constitution and reactivity have been diligently studied, economic appraisals have tended to direct the commercial work to the production of the more expensive, but less used, chemicals.

To more effectively utilize coal, the invention takes advantage of a relatively newly developed technique generally known as ebullation" which is more particularly described in the Johanson U.S. Pat., Re. No. 25,770. In this patent, a liquid and a gas are reacted in a reaction zone in the presence of particulate solids contact material. With the solids maintained in random motion in the liquid it is possible to obtain a greatly improved reaction due to good contact, the limited pressure drop, and particularly due to the uniformity of temperature. It was found possible to hydrogenate coal in the presence of a catalyst as described in the above patent as well as to carry out other chemical reactions.

SUMMARY OF INVENTION The present invention primarily accomplishes a relatively low-pressure hydrogenation of the solid coal particles fed into the reactor as a slurry and in the absence of expensive catalysts with a conversion of better than 80 percent of the coal solids and a net oil production of greater than 50 percent.

In this invention it has been discovered that the solid ash particles remaining after the hydroconversion of the coal are suitable contact material for use in the reaction zone.

One of the important features distinguishing the ash-containing conversion system from a catalyst-containing conversion system is the lower investment required by the former. The ebullating pumps, some high-pressure piping, and the catalyst addition with withdrawal systems are all eliminated. Furthermore, the substantial cost of the initial catalyst charge and the cost of continuous catalyst replacements are totally eliminated.

DESCRIPTION OF DRAWING The following description of a preferred form of embodiment of the invention is based on the attached drawing illustrative thereof, which drawing is a diagrammatic view of essential process equipment for the conversion of coal to valuable liquid and gaseous end products.

DESCRIPTION OF PREFERRED EMBODIMENT A coal such as bituminous, semibituminous, or subbituminous coal or lignite, or a similar solid carbonaceous material such as shale, entering the system at 10 is first passed through a preparation unit generally indicated at 12. It is desirable to dry the coal of all surface moisture and to grind the coal to a desired mesh and then to screen it for uniformity. In accordance with my invention the coal should have a fineness of about I mesh and is preferably of relatively close sizing, i.e., all passing 50 mesh and not less than 80 percent retained on 200 mesh. However, it will be observed that the preciseness of size may vary between different types of coals, lignite and shale.

The coal fines discharge at 14 into the slurry-mixing tank 16 where the coal is blended with a slurry oil indicated at l8 which, as hereinafter pointed out, is preferably made in the system. To establish an effective transportable slurry, the ground coal should be mixed with about an equal weight of oil but amounts of up to parts of oil per part of coal can be desirable.

The coal-oil slurry at 20 is then pumped at 21 through the heater 22 to bring the slurry up to a temperature between about 600 and about 950 F., and the desired pressure, such heated slurry then discharging at 24 into the reactor feed line 26. Makeup hydrogen is introduced from line 28 and mixed with recycle hydrogen in line 42, and introduced into reactor feedline 26. In a separate embodiment, makeup hydrogen can also be injected into the slurry oil steam before heater 22.

The combined hydrogen and coil-oil slurry then enters one or more reactors 30, passing upwardly from the bottom at a rate and under pressure and at a temperature to accomplish the desired hydrogenation.

By concurrently flowing streams of liquid and gasiform materials upwardly through a vessel containing solid particles, the solid particles are placed in random motion within the vessel by the upflowing streams. A mass of solid particles in this state of random motion in a liquid medium and also in contact with a gaseous medium is described as "ebullated." The dense ash resulting from coal decomposition reaches an equilibrium level in the reactor. At this level of equilibrium, the rate at which the particulate solids are formed from the conversion of the coal equals the rate at which the particulate solids are carried out of the reaction zone.

It is a relatively simple matter to determine for any ebullated process the range of throughput rates of upflowing liquid which will cause the mass of solid particles to become expanded while at the same time placing them in random motion. However, when fine particles such as ash comprise the bed, a concentration gradient exists along the length of the reactor with the highest concentration existing in the lower two-thirds of the vessel and the lowest concentration at the outlet.

In contrast to processes in which the fluid streams flow downwardly or upwardly through a fixed mass of particles. the spaces between the particles of an ebullated mass are thus large with the result that the pressure drop of the liquid flowing through the ebullated mass is small and remains substantially constant as the fluid throughput rate is increased. Thus, a considerably smaller consumption of power is required for a given throughput rate. Moreover, the ebullated mass of particles promotes much better contact between the coal fines and gasiform streams than with any fixed bed process. Under these conditions a significantly greater fluid throughput rate carrying the coal fines may be used without impairing the desired degree of contact than if conventional downflow or upflow through a fixed bed of contact particles is used.

Moreover, solid materials will pass through an ebullated bed where it would otherwise plug a fixed bed. Additionally, the random motion of particles in an ebullated mass causes these contact particles to rub against each other and against the walls of the vessel so that the formation of deposits thereon is impeded or minimized. The scouring action helps to prevent agglomeration of the contact particles and plugging up of the vessel. This effect is particularly important where relatively inert or noncatalytic particles are employed and maximum contact between coal fines, hydrogen and the contact particles is desired. Here the contact surfaces are exposed to the reactants for a greater period of time before becoming fouled or inactivated by foreign deposits.

Preferred reactor operating conditions are in the range of 750 to 950 F. and between 500 and 3,000 p.s.i.g. Coal throughput is at the rate of l5-300 pounds per hour per cubic foot of reactor space with the yield of unreacted coal as char less than 10 percent of the quantity of moisture and ash-free coal feed. Under these conditions the liquid velocity is on the order of l to 30 gallons per minute square foot of horizontal cross sectional of the reaction zone.

The degree of hydrogenation from a single pass in reactor 30 is such that there is some ash and unconverted coal solids in the liquid stream 34. Stream 34 passes to a low-pressure flash system 35. From such a system, it is appropriate to remove gaseous products at 36, a middle oil at 37 and a bottoms at 38. As hereinafter described, some, or all, of this bot toms is recycled to the reactor 30.

The overhead effiuent stream 139 passing to high-pressure separator 40 is primarily gaseous and is virtually free of solid particles of contact material. From the separator 40 a gas stream 42, largely hydrogen, is removed and after purification and heating at 33 can be returned to the reactor 30 to supplement the hydrogen requirements. A liquid stream 44 from the separator 40 passes to the low-pressure recovery system 46.

The low-pressure separator 46 permits removal of a high B.t.u. gaseous product at 48 and a solids-free light oil at 50. A middle oil stream is moved at 52. A portion of the liquid from line 52 may be used to prepare the initial-coal slurry at 16.

if desired, solids may be purged from reactor 30 at 54.

The flashed reactor liquid from vessel 35 passes through line 38 to vessel 60 which is a solids separation system. A high solids concentration stream is rejected from the system through line 62. The low solids concentration stream, in line 61, is recycled via 18 to provide slurry oil. Part of this stream can be taken as product through line 64. There are instances where in order to control the velocity in the reactor to a desired level, part of the reactor liquid in 34 can be recycled through line 39 back to the reactor or injected into line 18 to be used as slurry oil.

Another mode of operation utilizes vacuum distillation of the high solids concentration stream 65 in vacuum still 70 to provide a vacuum gas oil in 73, part of which may be recycled as part of the slurry oil in line 18 and part withdrawn as product in line 71. Vacuum still bottoms are withdrawn through line 74 and can either be recycled via 18 or withdrawn as product in 72.

The process of this invention may be carried out under a wide variety of conditions. To obtain the advantages of this invention it is only necessary that the liquid, coal fines, and gasiform materials flow upwardly through a mass of solid particulate contact material at a rate causing the mass to reach an ebullated state. in each ebullated system, variables which may be adjusted to attain the desired ebullation include the flow rate, density and viscosity of the liquid and the gasiform material, and the size, shape and density of the particulate material. However, it isa relatively simple matter to operate any particular process so as to cause the mass of contact material employed to become ebullated and to calculate the percent expansion of the ebullated mass after observing its upper level of ebullation through a glass window in the vessel, or by radiation or acoustic permeability, or by other means such as liquid samples drawn from the vessel at various levels. in general, the gross density of the stationary mass of contact material will be between about 25 and 200 pounds per cubic foot, the flow rate of the liquid will be between about I and 20 gallons per minute per square foot of horizontal cross section of the ebullated mass, and the expanded volume of the ebullated mass usually not more than about double the volume of the settled mass and preferably only about 60 percent. It is vital to control the velocity of the fluids passing through the reactor so that the ash concentration within the reactor is higher than the feed. The ash concentration is to be controlled by selective recycle to be greater than 4 percent.

Whereas in our prior experience, it has been found that particulate solids of the type recognized as hydrogenation catalysts when used with the ebullated" bed gave high and worthwhile conversions of solid coal to liquid and gaseous products, it has now been found that there are many benefits gained by operating the coal conversion zone without externally supplied catalytic contact particles. As the coal is converted in the reaction zone, ash particles are produced. in this coal conversion, the ash is an autogenously produced noncatalytic contact particle suitable for creating improved coal conversions. Although the term noncatalytic is related to a material having inert qualities, which would notbe properly descriptive of the ash, such contact particles as herein described are considered by those skilled in the art as noncatalytic. By the use of the ebullated technique, it has been possible to maintain a concentration of autogenously produced contact particles, in the form of ash, in the coal hydroconversion zone. The ash particles provide contact surfaces on which free radicals can be quenched with hydrogen.

Additionally it has been discovered, as the following examples demonstrate, that the conversion of the coal to desired hydrocarbons is affected by the fractionations and separations to which the recycle of the liquid effluent from the reaction zone is subjected to prior to its being slurried with the coal. it is essential that the fractions of fractionated reactor effluent combined to form the recycle be free flowing at handling conditions with sufficient ash to maintain at least 4 percent in the reactor and to maintain the residuum level in the reactor.

Having thus described the invention in general terms,

reference is now made to the specific examples which have been carried out in accordance with the techniques of the present invention and which should not be construed as unduly limiting thereof.

EXAMPLE l Pittsburgh Seam coal as described in table I, is processed by passing the coal through a reactor operating at 850 F. and 2,250 p.s.i.g. hydrogen partial pressure. The operating condi- TABL'E I.PITTBBURGH BEAM COAL As received Dry basis Proximate analysis, percent:

Moisture- 1. 71 8. 19 8. 33 41. 89 42. 62 Fixed carbon 48. 21 49. 05

Total 100. 00 100. 00

Ultimate analysis, percent:

Moisture 1. 71 Carbon 73.00 74. 26 Hydrogen 5. 40 5. 49 Nitrogen. U. 1. 46 1. 49 Sulfur. 3. 96 4.03 Ash 8. 19 8. 33 Oxygen by diflerenc 6. 28 6. 40

Total 109. 00

tions and results are summarized in table ll along with a comparison of results obtained in the same reactor with l/l6 inches cobalt molybdate extrudates on alumina. Reactor liquid containing ash and unconverted coal is recycled along with heavy gas oil obtained by vacuum distillation of the reactor liquid stream. The ash concentration in the reactor is found to be about 5.1 percent. I

The yields show a slightly lower yield of liquid products and lower hydrogen consumption of the noncatalytic case. The lower hydrogen consumption is reflected in the quality of the light products. This deficiency is rectified by further downstream treatment advantageously in that more selective catalysts and operating conditions can be used.

TABLE II Recycle streams: Vacuum gas oil Reactor quid Cobalt Ash molyhdate containing containing reactor reactor Operating conditions:

Temperature F.) 850 850 Pressure (p.s.i.g.) 2, 250 2, 250 Coal feed rate (lbs./hr./ft. reactor) 31. 2 31. 2 Ash concentration in reactor liquid (weight percent) 5. 1 5. 1 Recycle rate (lbs/lb. coal):

Vacuum gas oil 0. 83 1 Reactor liquid 4. 30 4 18 Prodilict distribution weight percent of d coa C1 9. 4 11. 2 12. 6 17. 2 22. 6 21.0 975 F. plus residuum oil benzene soluble 28. 3 25. 6 Benzene insoluble oil plus unconverted 13. 0 13. 2 8. 5 8. 5 4. 7 4. B 0. 6 0. 3 2. 7 l. 7 0.5 o. 7

Total (100 plus Hz reacted) 102. 9 104. 5

EXAMPLE ll The same Pittsburgh Seam coal described in table l is processed utilizing a low recycle ration of vacuum gas oil and a recycle of filtered liquid along with reactor liquid. The effect of this combination is to increase the heavy oil concentration in the reactor and allow for increased conversion of heavy oils to lighter products. The same effects in regard to product structure and hydrogen consumption are apparent. The important criteria is that the overall yield of liquid obtained in the ash containing reactor is not that much less than in the reactor with catalyst.

The results are summarized in table ill, which shows the comparison of an ash-containing reactor and a l/l6-inch cobalt molybdate extrudate containing reactor.

TABLE III Recycle streams: Vacuum lgas oil Reactor quid Filtered liquid Cobalt Ash molybdate containing containing reactor reactor Operating conditions:

Temperature F.) 860 850 Pressure (p.s.i.g.) 2, 250 2, 250 Coal feed rate (lbs./hr./ft.= reactor) 31. 2 31. 2 Ash concentration in reactor liquid (weight percent) 4. 5 4. 2 Recycle rate (lbs/lb. coal):

Vacuum as oil 0. 08 0. 10 Filtered quid...- 1.00 1. 28 Reactor liquid 4. 05 2. 79

Prodiict distribution weight percent of dry coa 11. 4 9. 9 14. 5 20. 3 97 29.1 32.7 975 F. plus residuum oil benzene soluble 20. 7 15. 8 Benzene insoluble oil plus unconverted Total (100 plus Hr reacted) 103. 5 104. 7

EXAM PLE iii A severity operation is carried out on Pittsburg Seam coal as described in table l where the recycle streams include vacuum gas oil, filtered liquid. vacuum bottoms and reactor liquid. The increased conversion is to be noted. for both the catalytic and ash-containing reactors. Table iV shows a comparison of an ash-containing reactor and a l/l6-inch cobalt molybdate extrudate containing reactor.

TABLE IV Recycle streams: Vacuum gas oil Reactor l quid Vacuum bottoms Filtered liquid Cobalt Ash Molybdate containing containing reactor reactor Operating conditions:

Temperature F.) 850 850 Pressure (p.s.i.g.). 2, 260 2, 250 Coal feed rate (lbs./hr./it.-' reactor) 18. 7 18. 7 Ash concentration in reactor liquid (weight percent) 5. 2 5. 4 Recycle rate (lbs/lb. coal):

Vacuum gas oil 0.21 0. 13 Filtered liquid 0.99 1. 24 Vacuum bottoms 0. 25 0. 28 Reactor liquid 4 04 5 68 Prodilict distribution weight percent of dry coa gas 21. 0 13. 2 0 -400 F. 1iquids 2L7 23.6 400-997 F M. 8 32. 6 976 F. plus residuum oil benzene soluble 12. 4 7. 5 Benzene insoluble oil plus unconverted I Total plus H; reacted) 105.8 105. 4

An analysis of an ash formed in the reaction zone and serving as the contact particles is shown in table V.

TABLE V.ASH ANALYSIS [Dry sulfur analysis] Percent weight Pyritic sulfur l. 48 Sulfate sulfur 0. 11 Organic sulfur (difference) 0. 92

Total sulfur 2. 51

[Mineral analysis] a. slurrying said coal feed with a portion of the recycle liquid which is subsequently recovered from the process in rations of 0.1 to 1.0 pounds of coal per pound of oil; passing the coal-oil slurry upwardly through a hydrogenation reaction zone in the absence of a catalyst together with hydrogen at a coal feed rate between and 300 pounds per hour per cubic foot of reactor space, the liquid and gas velocity being such that the coal and contact particles, as hereinafter set forth, in the reaction zone are placed in random motion in the liquid;

maintaining the reaction zone under a pressure of between 500 and 3,000 p.s.i.g. and a temperature in the range of 750 F. to 950 F.;

. withdrawing an effluent from the upper part of the reaction zone and separating from said effluent normally gaseous materials and a liquid containing char and ash and unreacted coal;

. recycling a portion of said liquid, containing char, ash and unreacted coal to be used as said contacts particles to the reaction zone;

. converting the carbon in the coal. on a moisture and ash free basis, in excess of 80 percent with the net oil produc tion being greater than 50 percent.

2. The process of claim I wherein the hydrogenation of the coal autogenously produces the contact particles maingained in the reaction zone.

3. The process of claim 2 wherein said contact particles are ash.

4. The process-of claim 1 wherein the ash concentration within. the reaction zone is maintained in excess of 4 ercent by selective recycle of reaction zone effluent.

5. The process of claim 1 wherein the recycle consists of a portion of the liquid effluent, from the reaction zone, containing char, ash and unreacted coal and a portion of the vacuum gas oil obtained from the fractionation of the remaining portion of said liquid efi'luent.

6. The process of claim 4 wherein the recycle also includes a portion of a filtered low solids concentration liquid obtained from the fractionation of said remaining portion of said liquid effluent.

7. The process of claim 5 wherein the recycle also includes a portion of a vacuum bottoms obtained from the fractionation of said remaining portion of said liquid effluent.

8. In the process of hydroconversion of coal to hydrocarbons wherein the coal is preliminarily dried, ground and screened to provide a coal feed substantially moisture free having relatively close sizing, and said coal feed is slurried with a subsequently recovered slurry liquid hereinafter defined said slurry having from at least I to not more than l0 parts of slurry liquid per part of coal feed, and said slurry.

together with hydrogen-rich gas is passed upwardly through a reactor in the absence of a catalyst under temperature and pressure conditions to effect a substantial hydroconversion of the coal to liquid and gas hydrocarbons, the liquid effluent from said reactor being fractionated into a relatively heavy bottoms material and other liquid and gaseous products the improvement which comprises: using said heavy bottoms material as the slurry liquid; said slurry liquid containing at least 1 part per of normally char, unconverted coal solids and ash, whereby the concentration of char, unconverted coal solids and ash. in the reactor exceeds that of the slurry liquid. such char, coal solids and ash having such a concentration as to enhance the hydrocarbon yield over that ofa once through operation.

9. The process of claim 8 wherein the ash concentration in the reactor is at least 4 percent.

1 II t 

2. The process of claim 1 wherein the hydrogenation of the coal autogenously produces the contact particles maintained in the reaction zone.
 3. The process of claim 2 wherein said contact particles are ash.
 4. The process of claim 1 wherein the ash concentration within the reaction zone is maintained in excess of 4 percent by selective recycle of reaction zone effluent.
 5. The process of claim 1 wherein the recycle consists of a portion of the liquid effluent, from the reaction zone, containing char, ash and unreacted coal and a portion of the vacuum gas oil obtained from the fractioNation of the remaining portion of said liquid effluent.
 6. The process of claim 4 wherein the recycle also includes a portion of a filtered low solids concentration liquid obtained from the fractionation of said remaining portion of said liquid effluent.
 7. The process of claim 5 wherein the recycle also includes a portion of a vacuum bottoms obtained from the fractionation of said remaining portion of said liquid effluent.
 8. In the process of hydroconversion of coal to hydrocarbons wherein the coal is preliminarily dried, ground and screened to provide a coal feed substantially moisture free having relatively close sizing, and said coal feed is slurried with a subsequently recovered slurry liquid hereinafter defined, said slurry having from at least 1 to not more than 10 parts of slurry liquid per part of coal feed, and said slurry, together with hydrogen-rich gas is passed upwardly through a reactor in the absence of a catalyst under temperature and pressure conditions to effect a substantial hydroconversion of the coal to liquid and gas hydrocarbons, the liquid effluent from said reactor being fractionated into a relatively heavy bottoms material and other liquid and gaseous products the improvement which comprises: using said heavy bottoms material as the slurry liquid; said slurry liquid containing at least 1 part per 100 of normally char, unconverted coal solids and ash, whereby the concentration of char, unconverted coal solids and ash in the reactor exceeds that of the slurry liquid, such char, coal solids and ash having such a concentration as to enhance the hydrocarbon yield over that of a once through operation.
 9. The process of claim 8 wherein the ash concentration in the reactor is at least 4 percent. 